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For y≠0y \neq 0, the particular solution of the differential equation 2yex/ydx+(y−2xex/y)dy=02ye^{x/y}dx + (y - 2xe^{x/y})dy = 0 at the point (1, 1) is

Solution

✅ Correct Option: 1

We are given:

2yex/y dx+(y−2xex/y) dy=02ye^{x/y}\,dx + (y - 2xe^{x/y})\,dy = 0

Rearranging to express dxdy\frac{dx}{dy}:

dxdy=−(y−2xex/y)2yex/y\frac{dx}{dy} = -\frac{(y - 2xe^{x/y})}{2ye^{x/y}}

=2xex/y−y2yex/y= \frac{2xe^{x/y} - y}{2ye^{x/y}}

=xy−12ex/y= \frac{x}{y} - \frac{1}{2e^{x/y}}

The repeated appearance of x/yx/y suggests the substitution v=x/yv = x/y.


Let v=xyv = \dfrac{x}{y}, so x=vyx = vy.

dxdy=v+ydvdy\frac{dx}{dy} = v + y\frac{dv}{dy}

Substituting into the equation:

v+ydvdy=v−12evv + y\frac{dv}{dy} = v - \frac{1}{2e^{v}}

ydvdy=−12evy\frac{dv}{dy} = -\frac{1}{2e^{v}}


2ev dv=−dyy2e^{v}\,dv = -\frac{dy}{y}

∫2ev dv=−∫dyy\int 2e^{v}\,dv = -\int \frac{dy}{y}

2ev=−ln⁡∣y∣+C2e^{v} = -\ln|y| + C

Substituting back v=x/yv = x/y:

2ex/y+ln⁡∣y∣=C2e^{x/y} + \ln|y| = C


At x=1x = 1, y=1y = 1:

2e1/1+ln⁡∣1∣=C2e^{1/1} + \ln|1| = C

2e+0=C2e + 0 = C

C=2eC = 2e


2ex/y+ln⁡∣y∣=2e2e^{x/y} + \ln|y| = 2e

ln⁡∣y∣+2ex/y−2e=0\ln|y| + 2e^{x/y} - 2e = 0

ln⁡∣y∣+2(ex/y−e)=0\ln|y| + 2(e^{x/y} - e) = 0

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